Lamp outage indicating circuits



April 21, 1970 3,508,237

S. KIMMELMAN LAMP OUTAGE INDICATING CIRCUITS Filed Dec. 1967 2Sheets-Sheet 1 FIG. I.

l JJ w 4 FROM STOP LIGHT CONTROL SWITCH IN VENTOR SAMUEL KIMMELMAN BYATTORNEY April 21, 1970 s. KIMMELMAN LAMP OUTAGE INDICATING CIRCUITSFiled Dec. 1, 1967 2 Sheets-Sheet 2 FIG. 5. 6 f i ,m

| l T 1 2 I) 0) 6) 6) 6) 6) E 15 1 .1 /7 l 2/ 22l 1 zas FROM ac. SOURCETO LOAD LAMPS FIG. 6. L2;

INVENTOR SAMUEL K/MMELMAN AT TORNE Y United States Patent York FiledDec. 1, 1967, Ser. No. 687,356 Int. Cl. G081) 21/00 US. Cl. 340251 9Claims ABSTRACT OF THE DISCLOSURE A lamp outage indicating circuit forenergizing from a variable voltage DC. current source a group ofparallel connected lamps includes an electrical signal device controlledby relay contacts positionable by the ampere turn values of first andsecond coils of the relay, current flow from the source through the lampgroup being directed through the first coil in series therewith, and thesecond coil receiving current flow from the source separately from thelamp group so that the flows of current through the coils vary similarlywith changes in the source voltage and only the current flow through thefirst coil changes with outage of a lamp to give rise to therelationship of the respective ampere turn values by which the relaycontacts are positioned to cause the signal device to give a lamp outageindication.

This invention relates to a direct current electric circuit for flashinga plurality of signal lamps, at least some rf which are connected inparallel, and having an electrical signal device, such as a pilot lamp,for indicating it one or more of the signal lamps is out.

The invention is especially suited for the flashing lamp systems ofmotor vehicles, such as turn-signal systems. In these systems it isimportant for safety reasons that the operator of the vehicle be madeaware if one or more of the signal lamps is not functioning.

In motor vehicle flashing lamp turn-signal systems, the direction of aturn to be made is indicated by lamps mounted on the corresponding sideof the vehicle at the front and back, and such lamps, when energized,flash intermittently due to the action of a flasher switch in thecircuit leading to the lamps. A pilot lamp on the dashboard of thevehicle normally flashes with the signal lamps. The circuit foroperating the pilot lamp should be reliably sensitive to indicate to theoperator the failure of even one lamp in the system, for danger couldarise if a signal lamp was not functioning.

In a known motor vehicle flashing lamp circuit, the pilot lamp isenergized by a single coil relay which is sensitive to the level ofcurrent therethrough to the signal lamps. This relay is actuated at thehigher current level which exists when all the lamps are functioning,but does not similarly respond to the lower current level existing whenone or more of the lamps is out. Thus, the relay ordinarily operates toflash the pilot lamp in time with the flashing of the signal lamps solong as all the lamps are operative; but if one or more of the signallamps fails, the pilot lamp remains on or off, depending on whether therelay is normally open or normally closed.

Since the voltage of the usual motor vehicle power supply is subject tovariations, the current flow through the relay coil to the lamps issubject to corresponding variations. The greater the range of voltagevariation the more ditficult it is to discern the change in currentlevel that occurs when one lamp fails. In fact, when more than a veryfew signal lamps are in the circuit, the current change expectable fromvoltage variations may be equal to or greater than the change occurringwhen one of 3,508,237 Patented Apr. 21, 1970 the lamps fails. Forexample, in the 12 volt direct current systems now generally employed inautomobiles, the actual voltage fluctuates between about 10 and 15volts. If such a system has four parallel connected signal lamps which,for example, provide a circuit current of 4.0 amperes at an appliedvoltage of 12.8 volts, the reduction of the applied voltage to 10 voltswill drop the circuit current to 3.52 amperes with all lamps operating,as compared with a decrease of the circuit current to 3.30 amperes ifone lamp fails at a time when the actual applied voltage is 15 volts.Thus, in a system with only four such signal lamps, the relay forcontrolling energizing of the pilot lamp has to discriminate betweencircuit currents of 3.52 and 3.30 amperes, that is, a difference of only6.25%, if the pilot lamp is to indicate only a lamp failure and not anallowable voltage fluctuation. If the number of such lamps is greaterthan four, the circuit current with all lamps operating at an appliedvoltage of 10 volts is less than or equal to the circuit currentresulting from an applied voltage of 15 volts upon the failure of onelamp, so that the relay cannot discriminate between the allowablevoltage fluctuation and a lamp failure.

Therefore, the known circuit for operating motor vehicle signal lampswill not give a true indication of lamp outages if used with more thanfour active lamps and is not suitably reliable for more than threeactive lamps. Yet many motor vehicles are now equipped with fourturn-signal lamps on each side, and turn-signal systems having more thanfour lamps to a side could be desirable and may be required in thefuture.

Accordingly, it is an object of this invention to provide a circuit forenergizing a group of parallel connected lamps from a variable voltagesource of direct current, which circuit includes an electrical signaldevice or indicator, such as a pilot lamp, and is effective to indicatereliably by such signal device if one or more of the lamps is out whenthe number of lamps served is greater than that employed in known lampoutage indicating systems.

Another object is to provide such a circuit which will reliably indicatethe failure of even a single lamp irrespective of the number of lamps inthe circuit and of the voltage variations at the source.

Still another object is to provide a lamp outage indicating circuithaving the foregoing characteristics and which is especially suitablefor the flashing lamp systems of motor vehicles, such as turn-signalsystems.

According to this invention, a lamp outage indicating circuit forenergizing from a variable voltage DC. current source a group ofparallel connected lamps includes an electrical signal device, such as apilot lamp, controlled by relay contacts positionable by the ampere turnvalues of first and second coils of the relay which may be wound to buckor oppose each other on a common core, current flow from the sourcethrough the lamp group being directed through the first or load coil inseries therewith and the second or bucking coil receiving current flowfrom the source separately from the lamp group so that the flows ofcurrent through the coils vary similarly with changes in the sourcevoltage and only the current flow through the first or load coil changeswith outage of a lamp of the group to give rise to a re lationship ofthe respective ampere turn values of the coils by which the relaycontacts are positioned to cause the signal device to give a lamp outageindication.

In cases where the parallel connected lamps of the group are to beintermittently energized or flashed, for example, as in flashing lampsystems of motor vehicles, the load coil through which current flows tothe lamps is connected in series with a flasher switch for receivingsuch current through the latter, and the other or bucking coil may beconnected in parallel with the series connected flasher switch, loadcoil and lamp group, or in parallel with the load coil and lamp group,or in parallel with only the lamp group.

In preferred circuits according to this invention, reliable indicationsof lamp outage are obtained, irrespective of the number of lamps in thecircuit and irrespective of the number of such lamps that may be out, bycon meeting the bucking coil of the relay in series with the relaycontacts and the signal device, and in such preferred circuits the relaycontacts may be either normally open or normally closed.

In circuits according to this invention for indicating lamp outage inflashing turn-signal system of motor vehicles, the signal device may beconstituted by a single pilot lamp for indicating a lamp outage ineither of the groups of signal lamps for signaling turns in the left andright directions, or two pilot lamps may be provided for indicating alamp outage in the respective groups of turn signal lamps.

Further, in circuits according to this invention, the relay with a loadcoil and a bucking coil may have normally open and normally closedcontacts connected to respective pilot lamps to indicate the properoperations of all of the load lamps or the failure or outage of one ormore of the load lamps. In such circuits, the two pilot lamps forrespectively indicating proper operation and outage of the load lampsmay be mounted behind differently colored lenses or mounted behind acommon lens and be of different colors to provide correspondinglycolored indications of proper lamp operation and of lamp failure oroutage.

The above, and other objects, features and advantages of the invention,will be apparent in the following detailed description of illustrativeembodiments thereof which is to be read in connection with theaccompanying drawings, wherein:

FIG. 1 is a schematic diagram of a motor vehicle flashing turn-signalsystem having a lamp outage indicating circuit according to thisinvention;

FIG. 2 is a schematic diagram showing a modification of a portion of thesystem illustrated by FIG. 1;

FIGS. 3 and 4 are views similar to that of FIG. 1, but showing otherembodiments of this invention provided with separate pilot lamps toindicate outage of a signal lamp in the groups of lamps for signalingturns in the right and left directions;

.FIG. 5 is a schematic diagram showing the application of a lamp outageindicating circuit in accordance with this invention to a simple systemfor energizing a number of parallel connected lamps; and

FIG. 6 is a schematic diagram illustrating a modification of a portionof the circuit shown by FIG. 5.

Referring to FIG. 1 in detail, it will be seen that, in the flashingturn-signal system for a motor vehicle, as there shown, the direction ofa turn to be made is signaled by the selective flashing or intermittentenergization of a plurality of lamps 10A and 10'A mounted on the rightside of the vehicle at the front and back thereof, or of a plurality oflamps 10B and 10B similarly located on the left side of the vehicle,which lamps all have given or predetermined resistances so as to passcurrents dependent on the voltage imposed thereon.

The selection of the group of signal lamps to be energized for signalinga turn is effected by a turn-signal switch 11 of conventional designhaving movable contacts 12A and 12B that are alternately movable, byselective manual actuation of the switch, from the rest positions shownin full lines on FIG. 1 to the actuated positions shown in broken lines.As is known. each of movable contacts 12A and 12B may be automaticallyreturned to its rest position in response to rotation of the steeringwheel upon completion of a turn in the direction corresponding to thecontact 12A or 12B. When in their rest positions, movable contacts 12Aand 12B establish conductive bridges between fixed contacts 13A and 14Aand fixed contacts 13B and 143, respectively. Signal lamps 10'A at theright-rear of the vehicle are connected in parallel between contact 14Aand ground, and signal lamps 10'B at the left-rear are similarlyconnected in parallel between contact 14B and ground. Contacts 13A and13B are both connected through a brake actuated switch 15 and, ifdesired, through a series connected ignition switch 16 to one terminalof a D.C. current source 17 having its other terminal connected toground The source 17 may be the usual storage battery of the motorvehicle, which source has a variable voltage, for example, a voltagevarying between 10 volts and 15 volts for a 12 volt D.C. current system.Thus, whenever the vehicle brakes are applied to close switch 15, therear signal lamp 10A and/or 10'B having the associated movable contact12A or 123 at its rest position are energized to provide a stop signal.

When in their actuated positions, contacts 12A and 12B establishconductive bridges from fixed contacts 18A and 18B to fixed contacts 19Aand 19B and also contacts 14A and 14B. Signal lamp 10A at theright-front of the vehicle is connected between contact 19A and ground,and signal lamp 10B at the left-front is similarly connected betweencontact 19B and ground. Thus, when contact 12A is actuated, all of thelamps 10A and 10A at the right side of the vehicle are connected inparallel to contact 18A and, when contact 12B is actuated, all of thelamps 10B and 10'B at the left side of the vehicle are connected inparallel to contact 18B.

Contacts 18A and 18B are connected through a flasher switch 20, and alsoif desired through ignition switch 16, to D.C. current source 17. Theflasher switch 20 may be of the type disclosed in US. Patent No.3,090,851 or in US. Patent No. 3,153,125, both issused to L. Strauss et2.1., or of any other type of switching device adapted to pass discreteintervals or pulses of current when connected to a D.C. current source.In the embodiment shown on FIG. 1, flasher switch 20 is of a type havingnormally open contacts with a parallel connected heating resistance 29which periodically causes closing of the contacts. Thus, when eithercontact 12A or contact 12B is moved to its actuated position, theassociated signal lamps 10A and 10'A at the right side of the vehicle orthe associated signal lamps 10B and 10'B at the left side of the vehicleare flashed or intermittently energized to signal turn in thecorresponding direction.

In order to indicate outage or failure of any of the turn-signal lampswhen turn signal switch 11 is actuated to cause flashing of such lamps,the circuit shown on FIG. 1 further generally comprises an electricalsignal device 21, which may be in the form of a pliot lamp, as shown,and a relay 22 for controlling operation of pilot lamp 21.

In accordance with this invention, relay 22 includes a first or loadcoil 23, a second or bucking coil 24, and contacts 25 and 26 which arepositionable relative to each other by the respective ampere turn valuesof coils 23 and 24 and interposed in a circuit for energizing pilot lamp21. Load coil 23 is interposed between contacts 18A and 18B and flasherswitch 20 so as to be connected in series with the group of parallelconnected signal lamps 10A and 10'A or 10B and 10'B to be flashed orintermittently energized from source 17 upon actuation of turnsignalswitch 11. Thus, the flow of current through coil 23, when flasherswitch 20 is closed, is the sum of the flows of current through theparallel connected signal lamps 10A and 10A or 10B and 10'B which arethen connected in the circuit by actuation of switch 11. Obviously,outage or failure of a lamp or lamps in the group of signal lampsconnected in the circuit by actuation of switch 11 will correspondinglyreduce the flow of current through coil 23.

The other or bucking coil 24 of relay 22 is, in accordance with thisinvention, connected to have a flow of current from source 17 conductedthrough such coil 24 sepa rately from the signal lamps A and 10'A or 10Band 10'B which are connected to the energizing circuit therefor byactuation of switch 11. Thus, the flow of current through coil 24 is notaffected by outage of a lamp or lamps in either group of signal lamps.However, the flow of current through bucking coil 24 and the flow ofcurrent through load coil 23 are similarly affected by variations in thevoltage at source 17.

In the arrangement of FIG. 1 which illustrates one of the preferredembodiments of the invention, bucking coil 24 is connected in a seriescircuit with relay contacts 25, 26 and signal lamp 21, which seriescircuit extends from a junction 27 between ignition switch 16* andflasher switch 20 to ground, and contacts 25, 26 are normally open.Thus, current flows through coil 24 and pilot lamp 21 is energized onlywhen movable contact 25, which may be carried by a biased armature ofrelay 22, is displaced from the position shown to engage fixed contact26.

Coils 23 and 24 are arranged, for example, by being oppositely wound ona common core 28, so that their respective ampere turn values, that is,the magnetic fluxes resulting from the flows of current through coils 23and 24, will oppose or buck each other. Accordingly, contacts 25 and 26will be closed or retained in a closed position for energizing pilotlamp 21 only when the difference between, or the net ampere turn valueof, the ampere turn value of load coil 23 (hereinafter referred to as ATand the ampere turn value of bucking coil 24 (hereinafter referred to asAT is at least as large as the minimum magnetic flux (K) required topull in the biased armature carrying contact 25. The condition requiredfor closing of normally open contacts 25, 26 and for maintaining suchcontacts in closed position may be expressed as:

The number of turns T in load coil 23 and the number of turns T inbucking coil 24 are selected so that condition (I) is achieved uponclosing of contacts 25, 26 only if all of the signal lamps 10A and 10Aor 10B and 10B then connected in the flashing circuit are functional,and so that ATL-ATB K when the flow of current through load coil 23 isreduced in response to outage or failure of even one, or some otherselected minimum number of the signal lamps in the group thereof thenconnected in the flashing circuit. Obviously, in selecting the numbersof turns T and T consideration must be given to the ratio of the currentflow through the load coil 23 to the current flow through the buckingcoil, which ratio is dependent, at least in part, on the number ofparallel connected signal lamps in each group thereof to be connected inthe flashing circuit by actuation of switch 11. For example, if each ofsuch groups of signal lamps contains four lamps, as in the embodiment ofFIGS. 1, and if the current flow through pilot lamp 21 is assumed to beequal to that through each signal lamp, then, so long as flasher switch20 is in its closed condition with one of the groups of signal lampsconnected in the flashing circuit, the flow of current through coil 23to the four parallel signal lamps 10A and 10A or 10B and 10'B will beapproximately four times as great as the flow of current through coil 24to the single pilot lamp 21 upon closing of relay contacts 25 and 26.

If the signal lamps and the pilot lamp are assumed to be types eachhaving a current flow therethrough of 1 ampere when a voltage of 12.85volts is impressed thereon, the current flow through each lamp will varybetween .88 amperes and 1.1 amperes, that is a difference of .22amperes, for voltage variations between 10 and 15 volts, respectively.Thus, in the case where four signal lamps are included in each group tobe connected to the flasher circuit, the flow of current through loadcoil 23 to such signal lamps will vary by .88 amperes for a voltagevariation between 10 and 15 volts, while the same voltage variation willproduce a similar, but smaller variation of .22 ampere in the flow ofcurrent through bucking coil 24 to the single pilot lamp 21. Since, for

any voltage variation at the source of DC. current, the change in theflow of current through load coil 23 is greater than the change incurrent through bucking coil 24 by a factor substantially equal to thenumber of lamps, the numbers of turns T and T must further be selectedin relation to the number of signal lamps to ensure that an allowabledecrease in source voltage does not decrease AT -AT B to less than K,while all signal lamps are functional and thereby cause an erroneousindication of lamp outage. Thus, AT AT with one which can be solved togive T /T +5 N or N T /T +5 Further, it is desirable that AT AT resultin positive net values, that is, AT AT when all signal lamps arefunctional. This condition is satisfied when (IV). It is even desirablethat AT AT when one signal lamp is out, and this condition is satisfiedby making N T /T +l (V).

For the illustrated example having four signal lamps (N=4) in each groupto be connected to the flashing circuit, T /T should be less than 4(Equation IV) and preferably less than 3 (Equation V). Further, theexact turns ratio should be selected, or a suitable resistance should beinterposed in series with either the coil 23 or the coil 24, or theresistance or bias of the relay armature against being pulled-in toclose contacts 25, 26 should be selected so that, for actual sourcevoltages varying between 10 volts and 15 volts, as expected, thecondition of Equation I above is always satisfied with all signal lampsfunctioning and the condition of Equation II above is satisfied wheneverone, or some other selected minimum number of the signal lamps is out.

Of course, if the pilot lamp has current characteristic different fromthe current characteristics of the signal lamps, Equations III, IV and Vwill be be correspondingly changed.

The operation of the circuit of FIG. 1 is as follows:

Assuming that ignition or master switch 16 is closed, manipulation ofswitch 11, for example, to move contact 12A to its actuated position,will cause a flow of current to occur through heating resistance 29 offlasher switch 20. After a predetermined period of such heating, theflasher switch contacts close to pass a flow of current through theclosed contacts and to signal lamp 10A and 10A to light the latter or asmany of them as are functional. Since relay contacts 25, 26 in serieswith coil 24- are normally open, initially there is no current flowthrough coil 24, and the ampere turn value of coil 23 is not bucked atall. If the number of signal lamps that are functional is sufllcient toresult in a value of AT greater than K, the relay armature is pulled-into close contacts 25, 26, with the result that a flow of current passesthrough coil 24 to pilot lamp 21 for lighting the latter. If all signallamps are functional the simultaneous flows of current through coils 23and 24 result in the condition AT =AT ZK, so that the relay contacts 25,26 remain closed so long as the contacts of flasher switch 20 areclosed. When the flasher switch contacts are closed, relatively littlecurrent passes through the high, parallel resistance of heater 29 sothat progressive cooling occurs until the flasher contacts again open.When the flasher switch opens to deenergize signal lamps 10A and 10'A,current flow through coil 23 is interrupted and the initially continuedflow of current through coil 24 would tend to cause a reversal of thepolarity of the net magnetic flux, but in effecting such reversal ofpolarity the net flux drops toward a zero value so that relay contacts25, 26 open to deenergize pilot lamp 21. Thus, so long as all signallamps connected in the flashing circuit are functional, pilot lamp 21will flash substantially in time with the flashing signal lamps.

If one signal lamp is out, relay contacts 25, 26 are closed in responseto the initial flow of current through load coil 23. However, whencontacts 25, 26 close, the resulting flow of current through buckingcoil 24 to pilot lamp 21 achieves the condition AT =AT K, so thatcontacts 25, 26 will again open even though the contacts of flasherswitch remain closed. Thus, in response to outage of a single signallamp, pilot lamp 21 will be made to flicker and thereby indicate suchoutage.

If several of the signal lamps are out, either one of two conditions maybe encountered. Firstly, the number of signal lamps remaining functionalmay be so small as to result in an initial flow of current through coil23 that is insufficient to create the condition AT K necessary for evenmomentary closing of contacts 25, 26 and the described flickeringillumination of pilot lamp 21, so that the latter will remain dark.Secondly, if the initial flow of current through coil 23 is sufficientto cause closing of contacts 25, 26, it may still be of such smallmagnitude that AT -AT occurring on closing of contacts 25, 26 tends toresult in a negative net value greater than K. However, in tending toeffect reversal of the polarity of the net flux, the latter drops towarda value of zero and thereby causes opening of contacts 25, 26 tointerrupt the circuit through coil 24 to pilot lamp 21. Thus, flickeringof pilot lamp 21 again occurs to indicate outage of more than one signallamp, even though coils 23 and 24 are wound on the same core 28 and thenet flux resulting from AT being greater than AT may be larger than thenet flux required to pull in the armature and close contacts 25, 26.

It should be noted that, with the flasher switch 20 having normally opencontacts, as shown on FIG. 1, the resistance of heater 29 must besufficiently large in relation to the number of signal lamps 10A and10'A or 10B and 10'B to ensure that, when the flasher contacts are open,the flow of current through heating resistance 29, and hence which isdivided among the paralleled signal lamps, will be substantially lessthan that required to light such lamps. Of course, upon closing of thecontacts of the flasher switch, such resistance 29 is shunted by theclosed contacts and thus effectively removed from the circult of thesignal lamps which have substantially the full source voltage impressedthereon to light the same.

If desired, the flasher switch 20 and relay 22 can be convenientlyembodied in one assembly, as represented by the enclosing box in brokenlines on FIG. 1, which assembly has terminals X, Y and Z respectivelyadapted for connection to the source 17 through ignition or masterswitch 16, to the turn signal switch 11, and to the pilot lamp 21.Although the assembly 30 employs a conventional flasher switch 20 withnormally open contacts, a flasher switch with normally closed contactsmay be substituted therefor, in which case current flows therethroughimmediately upon actuation of the turn signal switch connected toterminal Y and, after a predetermined period, the normally closedcontacts of the flasher switch are opened for another predeterminedperiod, with the periodic opening and closing of the contacts beingrepeated cyclically to flash the signal lamps so long as the latter areconnected to the flashing circuit.

It is also to be noted that the relay 22 having normally open contacts25, 26 may be replaced by a similar relay having normally closedcontacts, for example, as in the case of the relay 22a shown on FIG. 2.As before, the relay 22a has a load coil 23a for connection in serieswith the parallel connected signal lamps so that the flow of currentthrough coil 23a is determined by the sum of the currents flowingthrough the signal lamps, and a bucking coil 24a, which may beoppositely wound on the same core 28a as coil 23a and is connected in aseries circuit with normally closed contacts 25a, 26a and the pilotlamp. Such series circuit extends from a junction 27a locatedintermediate the normally open contacts of flasher switch 20 and coil23a so that coil 24a also receives a pulsing or intermittent flow ofcurrent in response to the opening and closing of the flasher switchcontacts. It will be apparent that the flow of current through coil 24awill be separate from the flow of current through the signal lamps andthus not influenced by outage of a signal lamp, and that the flows ofcurrent through coils 23a and 24a will be similarly influenced byvariations of the source voltage.

In the case of the relay 22a, the number of turns T in load coil 23a andthe number of turns T in bucking coil 24a may be selected so that, whenall signal lamps are functional, the ampere turn value AT of load coil23a is substantially balanced by the ampere turn value AT of buckingcoil 24a, or at least so that in which K is the net ampere turn value ormagnetic flux required to open the normally closed contacts 25a, 26a.Further, the respective numbers of turns in coils 23a and 24a areselected so that upon outage of one, or some other predetermined minimumnumber of the signal lamps, there will be obtained the condition ATE-ATL K1 (VI thereby to open the contacts 25a, 26a.

As in the case of the relay 22, the numbers of turns in coils 23a and24a, or the resistance to relative movement of contacts 25a, 26a totheir open position, that is, the value of K are selected so that theconditions of Equations VI and VII are respectively satisfied when allsignal lamps are functional and when one or more signal lamps are out,irrespective of the acceptable variations of the source voltage.Further, the value of resistance 29 is selected so that, when turnselector switch 11 is in its neutral or non-actuated position, thecurrent through resistance 29, coil 24a, contacts 25a, 26a and pilotlamp 21 to ground will be limited by resistance 29 and the resistance oflamp 21 to a value which cannot cause heating of the flasher switch 20to a temperature at which the latters normally open contacts are made toclose. Further, such limited current through coil 24a will result in anampere turn value AT K that is, in a magnetic flux that is less thanthat required to overcome the spring bias of contacts 25a, 26a to theirnormall closed position. Thus, so long as turn signal or selector switch11 remains in its neutral position, the contacts of flasher switch 20remain open and contacts 25a, 26a of relay 22a remain in their normalclosed position.

When turn signal switch 11 is actuated, the parallel connected signallamps 10A and IO'A or 10B and 10B provide relatively lower resistancepath from junction 27a to ground and accordingly increase the currentflow through resistance 29 to a value that raises the temperaturesufliciently to close the contacts of flasher switch 20. The increasedcurrent flow through resistance 29, and

the correspondingly increased voltage drop across resistance 29,decreases the voltage impressed on pilot lamp 21 so that the latter isnot brightly illuminated until the contacts of flasher switch 20 areclosed.

Upon closing of the contacts of flasher switch 20, the battery voltageis impressed at junction 27a. If all of the connected signal lamps arefunctional, the ampere turn values of coils 23a and 24a are equal andopposite, that is, AT AT K so that contacts 25a and 26a remain closedand the pilot lamp 21 connected to terminal Z is flashed in timedrelation to the flashing of the signal lamps. If one or more of thesignal lamps are out, the resulting decrease of the flow of currentthrough coil 23a, without corresponding decrease in the current flowthrough coil 24a, causes AT -AT K with the result that contacts 25a, 26aare opened to extinguish pilot lamp 21. The opening of contacts 25a, 26aalso decreases the ampere turn value of coil 24a to zero and, before thecontacts 250:, 26a can close in the course of the decrease of the ampereturn value of coil 24a, the ampere turn value or flux of coil 23abecomes controlling, that is, AT K to maintain contacts 25a, 26a in opencondition, thereby to keep pilot lamp 21 in its extinguished condition.

In FIG. 1, the outage indicating circuit in accordance with thisinvention is associated with a single pilot lamp 21 which serves toindicate the proper functioning or outage of lamps in the two groups ofsignal lamp 10A and 10'A, and 10B and 10'B provided for signaling turnsin the right and left directions, respectively. However, outageindicating circuits in accordance with this invention may beincorporated in flashing turn-signal systems for motor vehicles whichhave two pilot lamps for respectively indicating outage of lamps in thegroups of signal lamps provided for signaling turns in the right andleft directions.

For example, as shown on FIG. 3, there is provided an assembly 30b of anormally open flasher switch and a relay 22b which is similar to therelay 22 in that it has a load coil 23b connected in series between theflasher switch and contacts 18A, 18B of turn signal switch 11, a buckingcoil 24b and normally open contacts B, 268 which are closed only when ATA T ZK. However, in the circuit shown in FIG. 3, bucking co-il 24b isconnected in series with contacts 25b, 26b and with two parallelbranches having pilot lamps 21A and 21B in series with diodes 31A and318, respectively, in a circuit that extends from contacts 19A and 19Bof turn signal switch 11 to ground. It will be apparent that, whenswitch 11 is manipulated to move either contact 12A or 12B to itsactuated position and thereby connect signal lamp 10A and 10B or 10B and10'B to the flashing circuit, the pulsing current flowing through loadcoil 23b is divided, at either contact 19A or 1913, and a portionthereof can flow through either pilot lamp 21A or 21B, respectively, andbucking coil 24b to ground upon closing of relay contacts 25b, 26b.Thus, the flow of current through bucking coil 24b is separate from theflows of current through the parallel connected signal lamps 10A and 10Aor 10B and 10'B, is not influenced by outage of such signal lamps. Onthe other hand, the flow of current through load coil 23b is dependenton the number of functioning signal lamps, and the flows of currentthrough coils 23b and 24b are similarly influenced by variations in thevoltage at source 17.

As in the case if relay 22, the numbers of turns in coils 23b and 24b ofrelay 22b and the resistance to closing of its contacts 25b, 26b areselected so that A TL'A T B=K when all signal lamps are functionalirrespective of variations in the source voltage, and so that wheneverone, or some other predetermined minimum number of the signal lamps isout.

The arrangement of FIG. 3 operates as follows:

Upon manipulation of switch 11, for example, to move its contact 12B toits actuated position, as shown in broken lines, left turn signalinglamps 10B and 10'B are connected in parallel to contact 18B and hence tothe flashing circuit, and simultaneously the series circuit containingpilot lamp 218, bucking coil 24b and relay contacts 25b, 26b isconnected to contact 183 by way of engaged contacts 12B and 19B. Whenflasher switch 20 closes, there is an initial flow of current throughload coil 23b to signal lamps 10B and 10B, which initial flow of currentresults in AT K so that contacts 25b, 26b are closed and current flowpasses from contact 19B through pilot lamp 21B, diode 31B, coil 24b andthe closed relay contacts to be ground. If all signal lamps arefunctional, AT AT =K so that contacts 25b, 26b remain closed for so longas flasher switch 20 is closed, whereby pilot lamp 21B is flashed intime with signal lamps 10B and 10'B to indicate that a left turn isbeing signaled and that all of the signal lamps provided for thatpurpose are functional.

It should be noted that flow of current through pilot lamp 21A andsignal lamp 10A to ground is blocked by diode 31A, thereby to preventlighting of pilot lamp 21A or of the signal lamp 10A in series therewithwhen contact 12A is in its rest position.

If one of signal lamps 10B and 10'B is out, the initial flow of currentthrough coil 23b is suflicient to close relay contacts 25b, 26b andtemporarily light pilot lamp 213. However, when the bucking flow ofcurrent through coil 24b occurs, AT AT K so that contacts 25b, 26b openand pilot lamp 21B goes out. Thus, so long as flasher switch 20 isclosed, pilot lamp 21B is made to flicker, thereby indicating outage ofa lamp in the group of lamps for signaling a left turn. If more than onesignal lamp is out, the result is again flickering of pilot lamp 21B, asdescribed above with respect to the arrangement of FIG. 1, unless thenumber of inoperative signal lamps is so large as to result in aninitial flow of current through coil 23b that is to small to causeinitial closing of contacts 25b, 26b, in which case, pilot lamp 21Bremains dark. Diodes 31A and 31B further ensure that, when contacts 25b,26!; are open in response to lamp outage, current cannot flow fromcontact 19B through lamps 21B, 21A and 10A to ground for even dimlyilluminating lamps 21A and 21B simultaneously.

When switch .11 is manipulated to signal a right turn by lamps 10A and10'A, the operation of pilot lamp 21A is similar to that described abovewith respect to pilot lamp 21B.

Referring now to FIG. 4, there is shown another circuit according tothis invention employing two pilot lamps 21'A and 21' B for indicatingproper operation or outage of the lamps provided for signaling turns inthe right and left directions, respectively. The circuit of FIG. 4includes an assembly 30 which, as shown, may be of the same type as thatemployed in FIG. 1, and thus includes a normally open flasher switch 20and a two coil relay 22 having normally open contacts.

In FIG. 4, the terminals X and Y of assembly 30 are connected in thesame manner as shown on FIG. 1, and the terminal Z, rather than beingconnected through a single pilot lamp to ground, as previouslydisclosed, is connected through a diode 31A and pilot lamp 21'A, and adiode 31B and pilot lamp 21'B, in parallel, to contacts 19B and 19A,respectively, of switch 11.

The operation of the circuit shown on FIG. 4 is as follows:

When switch 11 is manipulated, for example, to move its contact 12B tothe actuated position for signaling a left turn, and assuming that allof signal lamps 10B and ltl'B are functional, closing of flasher switch20 results in a flow of current through coil 23 to light signal lamps10B and 10B and to close relay contacts 25, 26- so that current alsoflows through coil 24, contacts 25, 26, pilot lamp 21'B and signal lampA to ground. Since all of signal lamps 10B and 10B are functional,contacts 25, 26 remain closed so long as flasher switch is closed, andthus pilot lamp 2.1B is flashed in time with signal lamps 10B and 10'B.Since the voltage drops across coils 23 and 24 are relatively small,approximately equal voltages are applied to opposite sides of pilot lamp21A upon movement of contact 12B to its actuated position and closing ofrelay contacts 25, 26, and thus pilot lamp 21'A is not illuminated.Further, pilot lamps 21'A and 21B are selected to be lit or renderedincandescent by substantially smaller flows of current therethrough thanare necessary to light signal lamps 10A and -10A or 103 and -10B. Thus,although pilot lamp 21'B is in series with signal lamp 10A, the reducedcurrent flow through that series circuit can light lamp 21B but not lamp10A.

If one or more of signal lamps 10B and 10B is out, such outage isindicated either by flickering of pilot lamp 21'B or by the failure ofthat pilot lamp to light, as described above with reference to FIG. 1.Of course, if switch 11 is manipulated to signal a right turn byflashing of signal lamps 10A and 10A, then the pilot lamp 21-A is eitherflashed in time with such signal lamps to indicate that they are allfunctional, or pilot lamp 21'A is made to flicker or not lit at all toindicate outage of one or more of the respective signal lamps.

The diodes 31'A and 31B ensure that, when contacts 25, 26 are open byreason of the outage of signal lamps upon the actuation of turn signalswitch 11, current will not flow from contact 19B through lamp 21'A,lamp 21'B and lamp 10A to ground, or from contact 19A through lamp 21B,lamp 21'A and lamp 10B to ground, to even dimly illuminate both pilotlamps simultaneously.

In all of the above described embodiments of the invention, the circuitsfor indicating lamp outage have been associated with flashing signallamp systems, specifically flashing turn-signal systems for motorvehicles. However, as shown on FIG. 5, a relay 22 such as has beendescribed above with reference to FIG. 1 may be employed with a pilotlamp 21 to indicate lamp outage in a simple circuit for energizingparallel connected load lamps 10 from a variable voltage source 17 ofDO. current upon closing of a master switch 16. As before, upon closingof switch 16, the flow of current to lamps 10 passes load coil 23 of therelay so that the current flow through coil 23 is dependent on thenumber of functioning lamps 10. The flow of current through bucking coil24 is separate from the current flows through lamps .10 and thus is notinfluenced by outage of any of such lamps. However, the flows of currentthrough both coils 23 and 24 are similarly varied in response tovariations of the source voltage.

When switch 16 is closed, the initial flow of current through coil 23 tolamp 10 causes contacts 25, 26 to close. If all lamps 10 are functioningso that AT AT 2 K, contacts remain closed and pilot lamp 21 is lightedcontinuously to indicate that all lamps are functioning. If one of lamps10 is out, so that, after the initial closing of contacts 25, 26 AT --ATK, contacts 25, 26 then open and there results a flickering of pilotlamp 21 to indicate the lamp outage. If the number of lamps that is outis so large that the flow of current through load coil 23 while contacts25, 26 are open does not result in AT K, there is not even momentaryclosing of contacts 25, 26 and pilot lamp 21 remains dark. If the outageof several of lamps '10 results in AT being greater than AT by at leastthe value of K, then the polarity of the net flux resulting from AT AT Kis reversed relative to the polarity of the initial flux when contacts25, 26 are open and AT K, and in the course of such reversal of polaritythe net flux becomes less than K to again open the contacts. Thus, evenwhen several lamps are out, pilot lamp 21 is made to flicker andreliably indicates such lamp outage.

Refering now to FIG. 6, there is shown a relay 220 in accordance withthis invention which may be employed in a system, for example, of thetype shown in FIG. 5, for lighting a pilot lamp 21C when all of the loadlamps are functional and for lighting a pilot lamp 21D upon outage ofone or more of the load lamps. Such pilot lamps 21C and 21D may bemounted behind differently colored lenses or be themselves of differentcolors and mounted behind a common lens to provide characteristic colorindications of the functioning of all load lamps and the outage of oneor more of the load lamps.

As shown, relay 220 includes a load coil 23c connected in series withthe paralleled load lamps to the variable voltage source of DC. currentso that the flow of current through coil 230 is dependent upon thenumber of load lamps that are functioning. Relay 220 further has abucking coil 240 connected in series with pilot lamp 210 between a fixedrelay contact 26c and ground, and a movable relay contact 25c connectedin parallel with coil 23c and normally engaging a fixed contact 1260which is connected through pilot lamp 21D to ground. The numbers ofturns T and T in coils 23c and 24c and the magnitude of the net magneticflux (K) required to move contact 250 from the position shown intoengagement with contact 260 are selected so that AT A T =K when all theload lamps are functional, and AT -A T K when one, or some other minimumnumber of load lamps is out.

If all load lamps are functional when the same are connected to the DC.current source through coil 23c, then the initial current flow throughcoil 23c obviously results in AT K and contact 250 is moved to engagecontact 260 and thereby light pilot lamp 210 by current flowing throughcoil 24c. Thereafter, AT AT =K so that contact 250 remains in engagementwith contact 26c to continue the illumination of pilot lamp 21C forindicating the proper functioning of all load lamps. However, if one orsome other predetermined minimum number of the load lamps is out, AT A TK so that, after the initial movement of contact 250 to contact 260,contact returns to its normal position against contact 1260, wherebythere is obtained a flickering of both pilot lamps 21C and 21D. If manyof the load lamps are out, so that AT K, the initial current flowthrough coil 230 with contact 250 spaced from contact 260 cannot causemovement of contact 250 away from contact 126050 that pilot lamp 21D iscontinuously lighted to indicate outage of many load lamps.

All of the above described embodiments of the invention have the buckingcoil of the relay arranged in series with a pilot lamp and contacts ofthe relay. Such arrangement is advantageous in that, even though thebucking and load coils are wound on a common core, in which case themovable relay contact may be displaced or pulled-in whenever a suitabledifference exists between the ampere turn values 'of the bucking andload coils, whichever is larger, the failure of several lamps will notresult in a false indication of all lamps being functional.

In all of the above described circuits according to this invention,pilot lamps have been provided for giving characteristic indications ofthe proper functioning and outage of the associated signal or loadlamps. However, it is obvious that such pilot lamps may be readily replaced by other types of electrical signal devices operative to givevisual or audible indication of the condition or the signal or loadlamps.

What is claimed is:

1. In a lamp outage indicating circuit for energizing from a DC. currentsource of variable voltage at least one group of several lamps havinggiven resistances to current flow and at least some of which areconnected in parallel, including means for connecting said lamps to saidsource and an electrical signal device for indicating a lamp outage, thecombination of a relay having first and second coils which generatecounteracting electromagnetic forces and having contact means positionedaccording to the relative ampere turn values of said coils and connectedwith said signal device for controlling the operation of said device,and respective means in said circuit for conducting current from saidconnecting means through said first coil and said group of lamps, inseries, and through said second coil in series with said contact meansand said signal device, but separately from said lamps, so that currentwill flow through said second coil only when said contact means isclosed, and so that flows of current through said coils will varysimilarly with variations of the voltage of said source and so that thecurrent fiow through said first coil, but not any current flow throughsaid second coil, is reduced by outage of a lamp of said group, therespective ampere turn values of said coils generated by flows ofcurrent therethrough at any of the normal voltages of said source beingsuch that said contact means is held in closed position when said groupof lamps is energized and all lamps of said groups are functional yetsuch that the force of said second coil overcomes the force of saidfirst coil so as to switch said contact means to open position therebycausing a lamp outage indication by said signal device if a lamp of saidgroup is not functional.

2. A lamp outage indicating circuit according to claim 1, said contactmeans being normally open, so that the force of said first coil willswitch said contact means to closed position when said group of lamps isenergized, said respective ampere turn values being such that if a lampof said group is not functional said contact means will be opened byoverriding force of said second coil to interrupt current flow throughsaid second coil and cause a flickering of said signal device by ensuingalternating sections of said coils.

3. A lamp outage indicating circuit according to claim 1, said contactmeans being normally closed and said respective ampere turn values beingsuch that they cause said contact means to remain in closed position soas to energize said signal device when all lamps of said group arefunctional, yet such that the force of said second coil will switch saidcontact means to open position to deenergize said signal device, and theforce of said first coil will then hold said contact means in openposition, if a lamp of said group is not functional.

4. A lamp outage indicating circuit according to claim -1, in which saidconnecting means includes flasher switch means operative to passdiscrete pulses of DC. current from said source to the lamps forflashing the latter.

5. A lamp outage indicating circuit according to claim 1, in which firstand second groups of said lamps are provided for alternate energizationfrom said source, and said current conducting means in the circuitincludes selector switch means actuatable to connect either group ofsaid lamps in series with said first coil.

6. A lamp outage indicating circuit according to claim 5, in which saidsignal device includes a pilot lamp energizable through said contactmeans when either of said groups of lamps is connected with said firstcoil.

7. A lamp outage indicating circuit according to claim 5, in which saidsignal device includes first and second pilot lamps respectivelycorresponding to said first and second groups of lamps, and said pilotlamps are connected in parallel with the respective grou s of lamps andin parallel with each other in a series connection with said second coiland said contact means so that, upon actuation of said selector switchmeans, any lamp outage in the group of lamps thereby connected with saidfirst coil is indicated by the respective pilot lamp.

8. A lamp outage indicating circuit according to claim 5, in which saidsignal device includes first and second pilot lamps respectivelycorresponding to said first and second groups of lamps, said pilot lampsbeing connected in parallel with each other in a series circuit withsaid second coil and said contact means so as to have substantially thevoltage at said source impressed at one side of each of said pilot lampswhen said contact means is in closed position, and means for impressingsubstantially the voltage at said source is impressed selectively at theother side of said first pilot lamp and at the other side of said secondpilot lamp upon actuation of said selector switch means to connect saidsecond lamp group and said first lamp group, respectively, in serieswith said first coil.

9. A lamp outage indicating circuit according to claim 1, in which saidsignal device includes first and second pilot lamps energizable toindicate the functioning of all of said lamps and the outage of a lamp,respectively, and said contact means includes normally closed contactsin series with said second pilot lamp to energize the latter in saidclosed position of the contact means and means for impressing normallyopen contacts in series with said first pilot lamp and which are closedin said open position of said contact means.

References Cited UNITED STATES PATENTS 1,726,423 8/1929 Churcher 340-251XR 2,127,887 8/1938 Rayburn 340--251 XR 3,171,096 2/1965 Murray et a1.340-251 XR 3,250,950 5/1966 Reiche 340251 XR JOHN W. CALDWELL, PrimaryExaminer D. MYER, Assistant Examiner US. Cl. X.R. 31582; 340

